1. Field of the Invention
The subject invention relates to methods and articles for facilitating the winding of a web on a cylindrical hub with the aid of a web leader, to wound web and web leader combinations, and to web leaders per se. Exemplary fields of utility of the invention include tape leader devices and techniques for magnetic recording and playback tape transports and film leader devices and techniques for motion picture projectors and other photographic film handling apparatus.
2. Description of the Prior Art
A large number of self-threading web transports, including magnetic recording tape and motion picture film transports, have become known and are in operation. Typically, these self-threading transports employ a leader which, being attached to the beginning of the web, is stiffer than the web itself and/or has other properties which render it more manageable by self-threading equipment. In some instances, leaders are utilized for signaling purposes in conjunction with an optical or other pickup in order to indicate to control equipment the beginning or completion of a recording, playback, or display operation, or for other known purposes.
In the overwhelming majority of cases, it has been found that the leader has to be thicker than the web in order to be able to perform its intended function. In consequence, when a web equipped with a typical prior-art leader is wound on a reel, spool or other winding facility having a cylindrical hub, there occurs a series of first bumps in a radial plane extending through the free end of the leader at the hub, as well as a second series of bumps coincident with a radial plane through the end of the leader to which the web is attached.
These bumps in the web roll have several known disadvantages, including the distortion of the roll from an ideal nearly perfect cylindrical configuration, the interference of the bump with the operation of peripheral roll drive equipment and, in the case of magnetic tape transports, the generation of signal distorting or degrading flutter.
I am aware in this connection of the U.S. Pat. No. 3,706,423, by Joseph J. Neff, issued Dec. 19, 1972 and proposing take-up and supply leaders being tapered toward their secured ends so that when these take-up and supply leaders are coupled to one another and wound about the reel hub, creases are not produced in the wound tape because of an abruptly changing significant thickness where the supply leader is secured to the tape and where the take-up leader is secured to the take-up reel hub. In practice, while workable in some instances, this prior-art approach still eventuates eccentricities and discontinuities in the wound web configuration.